1. Field of the Invention
The invention is directed to flocculant compositions which serve both as an absorbant and flocculant in high solids slurries, particularly slurries of fly ash.
2. Background Art
Coal fired energy plants produce large quantities of fly ash, a somewhat undefined composition which generally contains large amounts of silica but may also include numerous other inorganic compounds, and at times traces of organic compounds as well. The fly ash is often stored or transported as a wet solid (“saturated fly ash”) or a concentrated aqueous slurry, for use as an additive to cementitious compositions, as a filler in non-critical applications where filler makeup is less stringent, and for disposal as landfill. Due to its chemical makeup, saturated fly ash can be a serious contaminant. Fly ash because of its chemical makeup is considered a hazardous material by the Environmental Protection Agency. The physical gradation is heavily weighted toward silt and sand with a smaller portion of the composition of clay sized particles. Fly ash is highly dispersed particles with poor agglomeration moisture retention properties. When loaded in a rail car for transport to a waste disposal facility, the ash shifts, settles and perks water to the surface. The water that perks out is highly turbid with fly ash and can be spilled from the rail car while in transit. The invention is designed to absorb, flocculate, solidify the surface layer and to filter the highly turbid ash laden water to prevent an accidental discharge or spill from the rail car while in transit to the disposal facility. During storage and transit, despite the high solids content, some separation of fly ash and an aqueous phase occurs. This aqueous phase is very turbid, containing a large amount of suspended ash and dissolved (principally) inorganics, is corrosive, and can cause staining of surfaces which it contacts. The aqueous phase easily “sloshes” out or discharges through openings, cracks, rivets, drain holes, and the like, particularly during rail transit. During such transit, the vibration of the wheels against the tracks, particularly at rail joints, as well as acceleration, deceleration, and transit around curves maintains ash particles in suspension in an aqueous phase.
Typical ash management technique is to place a liner in an open top rail car, this liner has 4 flaps, each end and two in the middle that are folded closed and bungied to secure load while in transit to the hazardous waste disposal facility. While in transit the ash settles and highly turbid ash laden water perks or rises to the top, making its way out of the closed liner. Once on the surface of the liner it can be blown out of the car or sloshed out during stops and starts, shifting from front to back or side to side while in transit. It can also seek out the path of least resistance, making its way over the liner but still within the car seeking out any opening, rivet, cracked weld or drain hole in the bottom of the car. It's a requirement that no ash leave the rail car while in transit.
It would be desirable to reduce the propensity of water in high solids fly ash or fly ash dispersions to separate, and also to remove suspended particles from a separated aqueous phase or prevent their formation as a dispersed phase.